Subjects will be instructed to walk along a 17 m walkway in which two force plates are embedded. Speed will be measured by photoelectric beams located 3.06 m apart, midway along the walkway. Eight to ten walking trials will be averaged for each subject. Kinematic and kinetic variables will include hip, knee, and ankle angles and moments, in the sagittal, frontal and transverse planes. The setup and the analysis software that we used are the same as our collaborative group at the University of Delaware use.